As is know in the art, fuel injection systems are used to inject an amount of fuel into cylinders of an internal combustion engine. The fuel injection process is one of the most critical events in the preparation of air/fuel mixing in an internal combustion engine. It effects combustion quality and engine-out emissions. Electronic control units determine the amount of fuel to be injected into such cylinders and the time of such fuel injection and command the fuel injection system to provide such amount at such time. The amount of fuel to be injected into such cylinder is calculated by an engine control unit (ECU) as a function of the air quantity passing to the cylinder as measured by an mass air flow (MAF) sensor or indirectly measured by manifold absolute pressure (MAP) sensor. In one such system, the ECU determines the pulse width to turn on the injector to provide the desired amount of fuel to that cylinder; such systems are commonly called pulse width modulated (PWM). The constant amplitude pulse has a time duration, or fuel pulse width (FPW), related to the calculated fuel quantity. The ECU also determines the time at which such fuel is to be injected into the cylinder. The time of injection is such that the injection occurs at a proper engine crank angle associated with one of the cycles of a four-stroke engine, for example. That is, the time of injection, or targeting injection position, is crank angle based, while the quantity of fuel is time-based. There is a conversion provided by the ECU between crank angle based parameters and time-based parameters. The conversion is calculated based on engine speed. The ending location of fuel injection may be at either closed-valve or open-valve. More particularly, in port injection, closed-valve injection (CVI) strategy is targeting the end of injection (EOI) at closed-valve while the open valve injection (OVI) expects the end of injection (EOI) happens during intake valve open.
The fuel injection process is even more critical for the timing request for starting location of fuel injection in DISI stratified engine and camless engines. Optimized starting of fuel injection maximizes the formation of a fuel cloud around the spark plug in the time frame of spark release. The fuel injection pulse lasts from several milliseconds to dozens of milliseconds depending on design of injector, fuel rail pressure, cylinder volume, and engine conditions. In cold crank and start-up, it generally needs longer fuel pulses to get enough vaporized fuel into the port or cylinder to generate the proper fuel/air mixture for combustion.
As noted above, there is a conversion provided by the ECU between crank angle based parameters and time-based parameters. The conversion is calculated based on engine speed. We have recognized that there if there is any error in engine speed, such error introduces error into the delivered fuel injection position. The speed errors can be due to either measurement error or the speed variation. The invention provides an approach to compensate for the error due to rapid speed change in fuel injection during crank/start and engine speed transition like engine tip-in and tip-out in an internal combustion engine. The invention includes two methods of engine speed prediction. One is polynomial model based engine speed prediction
In accordance with the invention, a method is provided for determining fuel injection time scheduling in an internal combustion engine. The method includes calculating a fuel time schedule for the engine using a prediction of engine speed at the time of such fuel injection.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.